a. Field of the Invention
The present invention relates to a retrofocus-type lens system for single-lens reflex cameras and, more particularly, to an extremely compact retrofocus-type wide-angle photographic lens system comprising a smaller number of lenses.
B. Description of the Prior Art
As retrofocus-type wide-angle lens systems, those of six lens component configuration are known, for example, as shown in Japanese Pat. Publication No. 26133-1963 in which a first lens component is a positive meniscus lens, a second lens component is a negative meniscus lens, a third lens component is a positive lens of large thickness, a fourth lens component is a negative lens, a fifth lens component is a positive meniscus lens, and a sixth lens component is a positive lens. Known lens systems of the above-mentioned configuration, however, have the following disadvantages. That is, as the airspace between the second and third lens components is large, the lens system as a whole becomes large. Moreover, even when it is tried to design a lens system with still larger aperture or wider field angle, it is impossible to attain a lens system for which aberrations are corrected satisfactorily.
To eliminate the above-mentioned disadvantages, a lens system attained by further developing the above-mentioned lens systems is known as disclosed in Japanese Pat. Publication No. 45015-1972 U.S. Pat. No. 3,832,037). In this lens system, the third lens component, i.e., the positive lens of large thickness in the above-mentioned lens system according to Japanese Pat. Publication No. 26133-1963 is divided into two lenses, i.e., a negative lens and positive lens arranged by providing a slight airspace between each other, and those negative and positive lenses are arranged closer to the second lens component. Thus, the invention according to Japanese Pat. Publication No. 45015-1972 provides an extremely compact retrofocus-type wide-angle lens system for which aberrations are favourably corrected over a wide field angle.